Roblox has recently implemented something similar to this proposed bill, and it has issues. A major issue is that it has repeatedly put adults in child age brackets and vice versa, as well as the fact that it is easily bypassed, with one child drawing on their face with a marker and being put in the 21+ age bracket (source 1). The only real way to confirm one's age is through a government-issued ID. However, this imposes privacy and security issues, as demonstrated by a data leak that happened after Discord implemented ID-based age verification in October, where 2 million government IDs were leaked (source 2).
The bill claims that an operating system provider "shall not share an age signal with a third party for a purpose not required by the bill," yet the only thing that happens if they break this rule is that the distributor must pay a fine of up to $2,500 for every minor whose information gets leaked accidentally, and up to $7,500 for every minor whose information gets leaked intentionally. For massive corporations, like Microsoft and Apple, this does virtually nothing, but open-source, nonprofit operating systems, like Linux, will essentially be killed by this bill. Additionally, the bill does not state any form of protection for adults who get their information leaked.